Drier control



J. F. COBB DRIER CONTROL Jan. 20, 1948.

3 Sheets-Sheet 1 Original Filed May 8, 1937 Jan. 20, 1948.

J. F. COBB- DRIER CONTROL Original Filed May 8, 1937 3 Sheets-Sheet 2 3 Sheets-Sheet 3 J. F. COBB DRIER CONTROL Original Filed May 8, 1937 Jan. 20, 1948.

Patented Jan. 20, 1948 DRIER common James Forrest Cobb, Portland, reg., assignor to The Moore Dry Kiln Company of Oregon, a cor-' poration Original application May 8, 1937, Serial No. 141,504. Divided and this application February 25, 1942, Serial No. 432,220

. 4 Claims. 1

This invention relates to automatic control means generally. to automatic heat and pressure control means more specifically and .is especially applicable to automatic heat control means for a drying chamber, in which application it will be specifically illustrated in the following specification for the purpose of explaining the invention.

The present application is a division of my application Serial No. 141,504, filed May 8, 1937, entitled Drier control," now Patent No. 2,275,- 042.

An object of my invention is the provision of a device sensitive to conditions, of which a thermostat is a clear example, and so arranging the sensitive device that it will energize means to change the conditions that affect the sensitive device and will then serially energize otherwise independent means that will cumulatively aflect the conditions that influence the said sensitive device if required, by steps, particularly where the step influences are cumulative and independent of time.

Another object of my invention is to provide a pressure sensitive working device operatively mounted to energize one mechanism and, if required, serially energize another independent mechanism by spaced steps, in which case the effect of energizing the additional mechanism is cumulative. Pressure is here included as interchangeable with temperature in situations where thi is true.

Other objects will be apparent from the specification and are particularly pointed out in the. claims.

Drawings accompany and form a part of this specification and are directed to two applications of the invention to dry kiln installations, because the invention is especially valuable for that use though by no means so limited. To indicate other uses, it is shown connected to a hot water tank and a pressure container.

In the drawings,

Fig. I illustrates application of the invention to a dry kiln where motive power to operate atmosphere condition control devices is compressed air, and starting and stopping of the devices is controlled by a thermostat, which in this case will be considered to be a wet bulb thermostat;

Figure II represents a dry kiln in which the atmosphere condition control device is againa thermostat, but will be regarded in this view as a dry-bulb thermostat;

Fig.. III diagrammatically represents two means of adding heat to the contents of a cylinder in combination with a two step control of the heat applying means, energized seriatim by different degrees of expansion of a Bourdon tube. according to the general plan disclosed in Figs. I and II;

Fig. IV represents the application of seriatim control of two sources of supply or different capacities when applie to an elevated liquid tank, or other device within which static pressure of a controlled amount is desirable in the face of variable demand; and

Fig. V represents the application oi my air operated control system to a dry kiln employing two air operated valves.

The thermostats of Figs. I and II are for remote control and both drawings are diagrammatic since devices of this character are compact and dlfflcult to delineate clearly without a number of related views, which are not required with a diagram.

In Fig. I, 8| is a dry kiln structure defining a drying chamber 8IA, within which are tracks BIB that support a load of lumber on a truck, both of the latter being indicated by 40. In a subchamber 82 is a humidifier, for example a steam spray pipe 10. Steam of suitable pressure-temperature characteristics will be supplied to the spray pipe 10 by the pipe 1013 from a supply source not shown.

A kiln ventilation device. for example a cover 4|, is placed at some suitable location on the dry kiln ill and controls the ventilator duct A. Other devices are required for efficient operation of a dry kiln but have been omitted for the reason that they are well known and not directly concerned with this disclosure; the two described are concerned with control of the wet bulb temperature.

The term ventilation referred to in this application refers to air interchange betweenthe in-' Within the drying chamber BIA a wet bulb I1 is suitably located, connected by a capillary tube 2 to a pressure sensitive device such as a spring tube such as the spiral tube 3. Rigid with the spiral tube 3 and movable therewith along a temperature indicating path 6A is a control actuator 5, a contactor 6B having contacts I and 8. The inner end of the spiral coil 3 is made rigid with the stud 26A of the arm 26. The arm 28 is pivotally supported at the pivot 25 and movable by any suitable means, for example by the screw. 21 working in the nut 28, which is pivotally attached to the arm 26 at the end opposite to the pivot 25.

A link 3| is pivoted to the arm 26 at 29 and to the segment 33 by the pin 36, giving the segment 33 an appropriate arcuate path of movement by virtue of the mounting pivot 35. The segment 33 is provided with gear teeth 33A which mesh with the toothed pinion 32, hence the pointer 32A will indicate the setting of the device, which may be changed by manipulation of the knurled head Zli which is held in place by the mounting, 2|. The position of the spring tube 3 can be shifted by manipulation of the knurled head 20, and if properly calibrated with the dial scale 30, definite wet bulb temperature conditions in the chamber 8| A will be shown on the scale 3|], by the pointer 32A.

The knurled head 20 is manually manipulated until the pointer 32A, which is carefully calibrated to indicate the action of the tube 3, indicates a chosen point on the scale 30, in this case 140 deg. wet bulb temperature.

In Fig. I it will be assumed that before the wet bulb temperature of the drying chamber 8|A' reached the chosen point of 140 degrees as stated, that the steam spray apparatus 10, was discharging into the kiln by reason of the control valve I2A being open, which was rapidly raising the temperature and humidity, and at that point chosen on the scale, 140 degrees, the control actuator 5 contacted the stem 8 and raised the two discs ll) of the balanced valve from their seats, providing an egress from the pipe MB, indicated air while a valve, as In, is open, which is unimportant.

The motor l3 and the motor lever |3A control the ventilator cover 4| which is shown closed, with its open position indicated by dotted lines. The valve stems 8 and l are arranged to be raised by the arm 5 at temperature spaced in- V This is shown tervals, say for example 3 degrees. by an offset at 6B in the arm 5 but obviously it can be done by numerous equivalent structures.

It is desirable that a single, calibrated pres sure sensitive device be employed because it is nearly impossible to make two of them that will draw the same pressure or temperature curve,

though quite simple to calibrate an indicating de-= vice with a given tube.

kiln due to moisture in the wood drops a few del grees more than the set point, the valve stem 8 seats to close the valve Ill on its valve seat to build up pressure in the air line |2B, connecting with the valve motor I2, and to open the valve |2A, turning on the spray 10, which is an auxiliary means for maintaining a sufficient amount of moisture in the kiln.

In Fig. II, the same general principles are applied with electrical energy substituted for comby I 0A and NE, of contained air, under pressure,

that was greater in area than the restricted inlet 9|A; whereupon the pressure rapidly fell to zero and the spring |2C of the valve |2A asserted itself to close ofi the steam supply of the steam spray device 10.

Upon a further raise of wet bulb temperature, if it occurs, the arm 5 will move further to contact the stem 1 and raise the valve discs 9 from their seats which will de-energize the air motor |3 in the same manner, whereupon the weight I30, which is analogous to the spring IZC of the valve IZA, operates to open the ventilator 4| as shown by dotted lines in this fiigure, which will rapidly check any increase in wet bulb temperature.

Mounted in the air valve body 90 are two control means such as sensitive, preferably balanced, air valves Ill ands, which respectively control air supply to the tubes H3 and NB. These valves receive air supply from the tube 9| through the restricted orifices MA and MB respectively. When a valve such as 9 is unafiected by the arm 5 it will close by gravity and air pressure will build up in a tube such as I33 and an air motor 13 will move the lever |3A to close the vent cover 4|. increase of temperature in the kiln chamber has registered with an air valve stem such as 8, the corresponding valve I0 will be opened and the motor, in this case the valve air motor l2, will exhaust for the reason that air channels "IA and |0B have a. considerably greater area than the air. supply orifice 9|A. There is a small waste of When the arm 5 under the influence of an pressed air. Energy will be supplied from LI and L2, which is connected to a source of energy supply not shown. 62 is a bus-bar leading to the terminal 55 and a flexible cable 56 is insulated at 31 from the pressure sensitive device 3. It has two electrical contact members 5| and 58 which serially connect with mating contact members 52 and 59. Bus-bars 53 and 60 are very thin and flexible as is obviously necessary.

Contact of 5| and 52 energizes the solenoid 69, which closes the valve 54 and shuts off the steam supply by way of the conduit 54A to the heating coil 83. Should temperature continue to rise within the chamber of the kiln 8|A, a further movement of the pressure sensitive device 3, will cause contacts numbered 58 and 59 to come together, which will energize the solenoid 5? arranged to control the valve 50, which in turn controls the conduit 50A and supplies steam from a source not shown to the heating coil 80.

The valves 50 and 54 are normally opened and will beclosed only under the influence of electrical energy means such as the solenoids Bi and 51 when current is supplied through the connect ing means 53 and 53A as shown. Otherwise the views in this figure where the numbers are the same as in Fig. I have the same mode of operation as those in Fig. I, except that of necessity electrical operation is more abrupt and will ordinarily require relays which are not here shown because they are well understood. The temperature sensitive device or bulb II, in this viiiezv will be presumed to be a dry bulb thermos a Fig. III illustrates an application of my invention for the purpose of controlling heat within a closed vessel such as a cylindrical tank. To the left-hand of the center line in the middle of the drawing the apparatus is in all essentials the same as that shown in Fig. I so far as the temperature control apparatus is concerned; and to let pipe llll.

the right of the center line is found the cylindrical vessel I00, containing fluid furnished through an inlet conduit IIHA and provided with an out- Within the receptacle, there are two fluid heating means, the well known mixing valve connected to the conduit H2 and controlled by the valve 12A and the heating coil I09, which is supplied by the steam supply pipe I02A, controlled by the valve A, the valves being similar to those shown in Fig. I at I2A. No further explanation is deemed necessary as to their action.

Steam is supplied through I02 and/or IMA and condensate from thecoil His is drained out by the trap I04. The usual thermostat bulb or pressure generating apparatus I1, is present within the chamber or inclosure I and is associated with the pressure sensitive device 3 by means of the conduit 2A.

In Fig. IV, I have shown an elevated tank 43 which represents pressure due to static head or other means as distinguished from temperature Apparatus of the type shown to the left of the center line in this drawing, Fig. III, will be presumed to be present and associated with the device of Fig. IV, but has not been redrawn, to save repetition.

In this case, however, the conduit 2A which associates the container 43 with the pressure sensitive device 3 is open to the contents of the container without any pressure generating device or bulb, and reliance is had upon static pressure or pressure by any other means to cause appropriate movement of the element 5.

In this figure the conduit 4 and conduit 45 will be connected to a convenient fluid supply source not shown, and the valves 63A and 65, which are essentially the same as the valve IZA of Fig. I, are arranged to control these several means of supplying fluid to the container 43, the step control feature is present and its operation will be a function of demand. The conduit 4, with its appurtenances, will furnish a normal supply to maintain the fluid level substantially as shown, whereas an unusual demand will bring the conduit 45 into operation by pressure change as shown and the combined capacity of the conduits 4 and 45 will then be available to maintain fluid level or pressure within the container 43; and obviously the dial scale 30 may be calibrated in pounds per square inch, or in feet elevation where fluid pressure control is concerned.

I am aware that work has been done in this field. Patent No. 1,705,176 discloses a means of serially energizing separate means for controlling humidity or wet bulb temperature in a dry kiln by providing a delay equipment where, when'a thermostat with a single contactor reaches a given point, it will set apparatus in motion to first close a ventilator and afterwards, separate by a variable time interval, it will start a steam spray. I prefer my embodiment, however, because when the ventilator is. closed the natural water content of the wood seldom renders it necessary that the steam be turned on, though it is there for emergency use if required.

What I claim as new and desire to have secured to me by Letters Patent, is:

1. In a temperature control apparatus, a mounting therefor, a thermostat comprising a bulb, a pressure sensitive coil and tubing connecting the bulb to the coil, an actuator made rigid with said coil, a pivot attached to said mounting, an arm hinged on said pivot, said coil the other, whereby two different devices under control of said control means may be operated at different temperatures.

( 2. In a pressure control apparatus, a mounting therefor, a pressure sensitive coil with tubing connecting the coil with a pressure source, an actu ator made rigid with said coil, a pivot attached to said mounting, an arm hinged on said pivot, said coil being mounted on said arm, a plurality of independent control means for operating separate devices, a pressure gauge having a pointer operatively mounted to indicate the pressure to be controlled at said source and being operatively connected to said arm, a threaded adjustment means shouldered on said mounting and operatively connected to said arm for moving saidactuator in relation to said control means and said pointer of said gauge, said actuator being spaced farther from one control means than from the other, whereby two different devices under the control of said control means may be operated at different pressures.

3. In a temperature control system for a chamtemperature of said chamber, a coil connected by tubing to said bulb, an actuator made rigid with said coil, a pivot attached to said mounting, an arm hinged on said pivot, said coil being mounted on said arm, a temperature gauge having a pointer operatively mounted to indicate the temperature to be controlled at said bulb in said chamber, said pointer being operatively connected to said arm, a threaded adjustment means shouldered on said mounting and operatively connected to said arm for moving said actuator in relation to said control means, and said pointer of said gauge, said actuator being spaced farther from one control means than. from the other, whereby two different devices under control of said control means may be operated at different temperatures.

4. In a temperature control system for a cham-' ber, low pressure heating means in said chamber, a control device therefor, high pressure heating means therein, a control device therefor, independent control means for operating said devices, a thermostat comprising a mounting, a bulb sensitive to the temperature of said chamber, a coil connected by tubing to said bulb. an actuator made rigid with said coil, a pivot attached to said mounting, an arm hinged on said pivot, said-coil being mounted on said arm, a temperature gauge having a pointer operatively mounted to indicate the temperature to be controlled at said bulb in said chamber, said pointer being operatively connected to said arm, a threaded adjustment means shouldered on said mounting and operatively connected to said arm for moving said actuator in relation to said control means, and said pointer of said gauge, said actuator in relation to said control means, and said pointer of said gauge,

said actuator being spaced farther 11-0111 one con trol means than trom the other, whereby two dlflerent devices under control of said control UNITED STATES PATENTS Number Name 7 Date means may be operated at dlfl l nt temperatures. 1 63o 536 it M 31 1927 1,918,265 Hartwlg July 18, 1933 JAB/1E8 FORREST (1033- 1,920,440 Stewart Aug. 1, 1933 961,734 Powers June 14, 1910 REFERENCES CITE 1,731,315 Mueller 061, 15, 1929 The following references are of record in the 113071764 Lehn -u Nov. 23, 1926 me of this patent: 1 1,375,957

Thinn et a]. Sept. 6, 1932 

